This medication is used to:
Treat breast cancer that has spread to other parts of the body in men and women.
Treat early breast cancer in women who have already been treated with surgery, radiation, and/or chemotherapy.
Reduce the risk of developing a more serious type of breast cancer in women who have had ductal carcinoma in situ (DCIS; a type of breast cancer that does not spread outside of the milk duct where it forms) and who have been treated with surgery and radiation.
Reduce the risk of breast cancer in women who are at high risk for the disease due to their age, personal medical history, and family medical history.
Tamoxifen is in a class of medications known as antiestrogens. It blocks the activity of estrogen (a female hormone) in the breast. This may stop the growth of some breast tumors that need estrogen to grow.
Tamoxifen is usually taken once or twice a day with or without food. Take tamoxifen at around the same time(s) every day. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain anything you do not understand. Take tamoxifen exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.
Swallow tamoxifen tablets whole; do not split, chew, or crush them. Swallow the tablets with water or any other nonalcoholic drink.
If you are taking tamoxifen to prevent breast cancer, you will probably take it for five years. If you are taking tamoxifen to treat breast cancer, your doctor will decide how long your treatment will last. Do not stop taking tamoxifen without talking to your doctor.IMPORTANT WARNING:
Tamoxifen may cause cancer of the uterus (womb), strokes, and blood clots in the lungs. These conditions may be serious or fatal. Tell your doctor if you have ever had a blood clot in the lungs or legs, a stroke, or a heart attack. Also tell your doctor if you smoke, if you have high blood pressure or diabetes, if your ability to move around during your waking hours is limited, or if you are taking anticoagulants ('blood thinners') such as warfarin (Coumadin). If you experience any of the following symptoms during or after your treatment, call your doctor immediately: abnormal vaginal bleeding; irregular menstrual periods; changes in vaginal discharge, especially if the discharge becomes bloody, brown, or rusty; pain or pressure in the pelvis (the stomach area below the belly button); leg swelling or tenderness; chest pain; shortness of breath; coughing up blood; sudden weakness, tingling, or numbness in your face, arm, or leg, especially on one side of your body; sudden confusion; difficulty speaking or understanding; sudden difficulty seeing in one or both eyes; sudden difficulty walking; dizziness; loss of balance or coordination; or sudden severe headache.
If you forget to take a dose of tamoxifen, take the missed dose as soon as you remember it, and take your next dose as usual. However, if it is almost time for your next dose, skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one.
Tamoxifen is also used sometimes to induce ovulation (egg production) in women who do not produce eggs but wish to become pregnant. Tamoxifen is also sometimes used to treat McCune-Albright syndrome (a condition that may cause bone disease, early sexual development, and dark colored spots on the skin in children). Talk to your doctor about the possible risks of using this drug for your condition.